Word of mouth spreads much more quickly in this era of blogs, Facebook and Twitter, and if you're part of the online book community you have probably already read some rather breathless appreciations of Firebrand. If you're not, then it's a pleasure to introduce you to a new (to me) writer who has written a completely fresh and exciting fantasy for teenagers.

For those readers who like adventure combined with romance and are tired of the fangbang genre, meet Seth McGregor. Sixteen years old but with a prospective lifespan of centuries, Seth is one of the Sithe (pronounced "shee"). In other words, Seth is a fairy.

But don't stop reading; there is nothing "pink" about this young man. He is the red-hot firebrand of the title. Scottish Sidhe are tall, good-looking, skilled in warfare and woodcraft and faster than a human can conceive. They can also be brutal, especially to full-mortals, but they are fiercely loyal to their own people.

And although long-lived they are not immortal. A veil separates the Sidhe world from the mortal one, but Seth's older half-brother Conal has been exiled and the two have entered the human world through one of the Watergates and found themselves in the late 16th century.

Although Conal keeps his head down and practises only modest healing arts, this is a time of witch-hunts and he soon attracts unwanted attention. So the book begins dramatically with Seth aiming a crossbow at his beloved brother to save him from the torment of burning. It takes another 200 pages of backstory to bring us up to that moment, but what pages! And there are still almost as many to go before the end.

Seth and Conal are both the sons of Griogair, a Sidhe clan-leader. But Conal's mother is Leonaora, the leader's bonded partner, and Seth's is Lilith, who is one of the most powerful advisers to the Sidhe Queen, Kate NicNiven. As soon as he is eight years old, Lilith sends Seth to live in his father's dun, where he is effectively ignored until Conal comes home and befriends him.

This is definitely a book for the older end of teenage readers. Seth cheerfully loses his virginity at about 13, and has a colourful line in swearwords. In fact, although a shade romanticised, he is a credible, impetuous and loyal hero, trying to prove himself in his father's dun and willing to fight to the death for his brother.

The main trouble in the Sidhe world comes from the court of Queen Kate: she wants to destroy the veil that keeps them hidden from mortals. And it's a dangerous and slippery thing, that veil. Time doesn't stay the same on both sides and, as in many Celtic myths, a short visit on the faerie side can send mortals back to find generations have passed since they left.

Queen Kate is the enemy of the two brothers we care about, and a formidable one. We are going to hear a lot more about her because Firebrand is  good news and bad  the first of a trilogy. Good because there is much more to come; bad because we have to wait for it.

Philip (pictured below) has created an utterly believable other world, where male and female are equals in arms. It is often stark and brutal but with moments of heartbreaking beauty. I haven't enjoyed a book in this genre so much since Susan Price's The Sterkarm Handshake.

Mary Hoffman's Troubadour is published by Bloomsbury.